Aircraft fuel pump



Jan.'e,1942. RR; @mis 2,268,805

' Origin'l Filed .'Jiy 1:5-, 1959 2 sheets-sheet 1l lll/ /2 44 /6` l fr no ,50

20e' z/o l z z zo@ 208 /92 l? zow /n l ILE 62 fw f6 l l' Jan. 6, 1942. R, R, CURTIS 2,268,805

l AIRCRAFT FUEL PUMP original Filed July ls, 1959 2 Sheets-Sheet 2 I 4 2 2f n 44 i Patented Jan. 6, 1942 AIRCRAFT FUEL PUMP Russell R.. Curtis, Dayton,

tis Pump Company, Dayton,

of Ohio Original Ohio, assignor to Cur- Ohio, a corporation application July 13, 1939, serial No. Divided and `this application March 4, 1940, Serial No. 322,203

6 Claims. (Cl. 74-509) This invention is a division of my copending application Serial No. 284,263, filed July 13, 1939.

particularly to mechanism for maintaining at a constant value the preselected pressure on the discharge side of the pump. v

An object of the invention is to provide the relief valve which connects Athe discharge and suction sides of the pump formaintaining the discharge pressure at a constant value, with a simple, and highly effective means for adjusting the loading of the valve whereby slight variations in the discharge pressure may be had without undue iineness in the adjusting mechanism.

Since it is highly important that the discharge pressure 'remain constant at the selected value to which it is adjusted, it is another object of this invention to provide a simple but effective. locking means which will positively lock the adjusting means in the position selected.

'Due to space restrictions in aircraft engine compartments, it is often necessary to mount the fuel pumps in rather inaccessible positions, and

' it is therefore another object of this invention to and relates to fuel pumps for aircraft engines,

so construct and arrangethe relief valve adjusting and locking mechanism that unlocking, adjusting, and relocking may be accomplished with several simple movements and with one hand.

Due to the fact that fuel tanks in aircraft are usually remotely located with respect to the rfuel pump, it is inevitable that the various angles which the'craft'assumes in flying, frequently alter the suction head on the intake side of the pump, and itis therefore another object of this y,

invention to provide simple yet accurate compensating means whereby this negative loading of the relief valve due to increased suction on the low side will not affect the. pressure on the discharge side for which the valve-has been adjusted. v

Other objects, advantages, and meritorious features will become apparent as the invention is described in greater detail, with reference to the drawings, wherein:

Fig. 1 is a vertical Isection through the pump taken at I-'I of Fig. 6 and bisecting the relief valve.

Fig.` 2 is a horizontal section taken- Fig.,1 to show the load adjusting nut.

at rz--z of Fig. 3 is a horizontal section taken at 3-3 of E Fig. l-to show the spring ringior holding the adjusting screw and related parts of the load adjusting means in place.

Fig. 1 to show the means foi-.locking the load adjusting screw.

Fig. 5 is a vertical fragmentary section, taken at 5`5 of Fig. 1 through the hinge of the bypass valve.

Fig. 6'is a vertical axial sectionthrough the pump taken at 6-6 of Fig, 1 showing the relief valve load adjusting mechanism, the suction head compensating mechanism, and the pumpdrive with itsv universal joint and seals.

Fig. '7 is ran axially transverse section taken throughFig. 6 at I-I to show the fuel seal ring and its special driving key.

Fig. 8 ris-a fragmentary view of the end of the pump shaft with the special driving key in place.

Fig. 9 is a side view,of the driving key.

Like numerals refer to like parts throughout the several views.

The pump body I2 is closed by a rear end wall I4 (see Fig. 6) and bored intermediate the ends to concentrically support the rear bearing I6,v

the front bearing I8, 'and the eccentrically bored pump cylinder 20.: The bearings and cylinder are preferably press tted one against the other in the body, the cylinder being additionally positioned and held against rotation by the pin "22 which extends through the body into a keyway- 24, preferably cut in the thicker portion of the cylinder wall. A cup shaped seal nut 2| having external threads 23 fitted to appropriate internal threads in the body I2 closes the open end of vthe body, and, together with resilient seal rings 25 and 21 holds the bearings and cylinal der in place-and provides against leakage between the seal nut and body.

The rotor 26 has a rear journal 28 and a front journal 30'rotatable in bearings I6 and I8 respectively. The rotor is hollowed for lightness and other reasons, a blind hole extending into the rear journal and through the rotor body and another into the front journal, a partition wall 32separating the inner ends of the two holes.

The rotor 2 6 is transversely slotted to slidably receive the three through-blades 34 (see Fig. 1) the cylinder bore and ends of the blades being so .formed that the blade ends contact the cylinder wall at all points in their rotation.

'Iy'he cylinder 20 has slots 36 and 38 positioned to align with ports 40 an :in the body I2.

With rotation in the-gspection of the arrow 44, Fig. 1, 40 becomesd; suction port and 42 the discharge port, butby merely removing the screws 46, Fig. 5, and turning the entire relief and bypass valve structure degrees von its Fig. 4 is a horizontal section-taken at 4-4 of 5;) vertical axis then replacing .the screws 46, the

y A donar 5s intermediate the ends holds the shaft from any appreciable axially outward movement. At the b-ottom of the hole in the front journal 38 adjacent the partition 32 is a driving member 58 which is secured in driving relation to the journal 30 by a plurality of relatively fine serreations 68 cut exteriorly on the member and heat treated to a high degree of hardness. Near the bottom, the interior surface of the hole in the journal may be left soft so that when the member 58 is pressed into the hole it will cut its own splines for joining the member and shaft in driving relation.

The outer end of the member 58 is transversely slotted to slidably receive a corresponding tongue in the Oldham vcoupling member 62., the outer end of the coupling member being transversely slotted at 90 degrees from its tongue to t slidably over the tongue 54 on the inner end of the drive shaft 58. The hole in journal 38 is enough larger than the outer diameter of the coupling 62 and shaft 58 to allow for considerable universal action of the shaft; y A pilot 64 on the seal nut 2| is adapted to enter a corresponding recess in the end of the engine bearing to eii'ect substantial concentricity between the engine and pump axes, the ange 66 being bolted to the engine by screws (not shown), whereby lubricating oil from the engine bearing may readily nd its way to the lOldham coupling member 62 and its cooperating parts.

A sealing ring 66, preferably of molded synthetic rubber or similar material is pressed .into a counterbored opening in the inner face of the seal nut 2|. The. ring 66 is of somewhat greater overall dimensions axially as `it comes from the mold than it is when in place as shown, whereby the face of the ring after assembly exerts' a considerable axial pressure against the end face of the journal 30, thereby effectively preventing any substantial amount of oil from the engine bearing or from the interior of the journal from escaping into the drain space 68 or other parts of the pump.

In order to prevent such leakage of fuel as may escape between the front bearing I8 and the front journal 38 from passing through and into the drain space 68, a highly effective seal must be provided. A spring ring 10 is snapped into a'groove in the outside of the journal 30 to hold a spring retaining washer 12, against which one end of the seal spring 14 bears.

The other end of the seal spring bears against a cup 16 which contains the packing ring 18. Ring 18 may preferably be made Vof synthetic rubber, the hole being of such size as to rit the outside of the journal 38 tightly so as to prevent leakage between the outside of the journal and the inside of the ring.

A seal ring 80 is compelled to rotate in unison with the journal 3|) by a key 82. Due to the fact that the wall of the journal is relatively thin, and the fact that the key must be removable to allow the spring retaining washer 12, cup 16,

and packing ring I8 to be assembled and removed, the key is of special construction.

Key 82 nts slidably in an annular groove 84 in the outside `of journal 30 (see Fig. '1) and comprises a rectangular strip bent to somewhat over a half circle and with enough resiliency to snap over the shaft diameter in the bottom of the groove. The upper'end of the strip is bent radially outward to compose the key part 86 which enters a keyway in the seal ring to drive it.

In'order to provide rotary driving connection of the key 82 with the journal 3D, the annular groove 84 is provided with a semicircular iniiection 88, in one edge and the upturned end 86 is widened as at 8B at this point to extend into this inection. Fig. 8 shows the outer end of the journal with the key in place as viewed in the direction of the arrow 9|, Fig. 7, while Fig. 9 shows the key viewed in the direction of the arrow 90 but removed from the journal.

Owing to the fact that externally to internally threaded together members are not conducive to extreme concentricity one with the other, and the further fact that slight distortion might ocl cur in pressing the seal seat into place, the seal seat is -not carried in the seal nut 2|, but on the end of a separate cup shaped seal housing 82 especially provided for the purpose.

The outside of the front bearing I8 should be finished truly concentric with the bore and the seal housing 92 tted closely thereover. The end face of the housing and the shoulder on the bear'- ing I8 which are in contact must both be faced to a true plane at right angles to the pump axis.

The external threads 94 which appear on the bearing I 8 are provided for pulling the bearing out when disassembling the pump, there being no` corresponding internal threads in the seal housing 92Which is clamped in place only by the seal nut 2|. The resilient seal rings 25 and 21 are made enough wider than the space they ultimately occupy that when the nut 2| is drawn solidly against the seal housing, the rings'will ybe under proper compression to make a tight joint.

The surfaces of the seal ring 80 and seal housing 92 which are in relatively rotatable contact are preferably finished to mirror-like smoothness and are kept in rubbing contact by the spring 14 which presses the cup 16 against the packing ring 18 which in turn'presses against the seal ring 8U. the parts 18, 12, 14, 16, 18, and 88 all having unitary rotation-with the journal 30.

It will be seen that any fuel escaping between the bearing I8 and journal 30 is caught in the seal chamber 96. The amount of leakage fuel escaping from chamber 96 is extremely small because of the tight lit of the packing ring 18 over the journal 30 and the spring pressure contact of the packing ring with the seal ring 88 all of which surfaces have unitary rotation, as well as the spring pressure contact of the highly nished metallic' contacting surfaces between the rotatable seal ring 80 and the stationary seat in the end of the seal housing 92;

Since some slight leakage may at times occur from the seal chamber into the drain space 68, the small hole 98 connects the space 68 with an annular groove |00 encircling the seal nut 2| which in turn is connected with the pipe tapped holes` |02 by the small holes |04. Opposite drain holes `are provided so that the pump may be mounted the other side up when desired.

One advantage of the combination seal land drive will be obvious. The rotatable seal ring 88,

' Space aaesos alignment. The arrangement possesses the further advantage that any fuel which gets past the rotatable seal ring 80 must dorso by moving radially inward against the action of `the centrifugal force of its own weight, whereas the escape past a seal which'is placed directly at the end of the bearing, as is usuallydone, is aided by the action of centrifugal force.

The exible sealing ring 66 permits direct communication between the oil supply of the engine bearing and the universal joint, whereby the joint is adequately lubricated, but prevents any considerable engine oil escaping into the drain 68 or back into the pump, such fuel as escapes into the drain space being prevented from mixing with the engine oil.-

The relief valve structure, provided for maintherein by the pin |64. The hole in the upper retaining washer |50 has a series of radial notches |66 (see Fig. .3 or 4) into any one of which the lower edge of the locking bar |62 may be entered as shown.- The washer |50 also has a key |68 at its outer edgewhich extends into the keyway |58 to hold the washer |50 from rotating.

The adjusting screw cap |10 when drawn tightly to thegasket |12, allows but a slight clearancebetween the inside of the cap and the top of the locking bar |62, whereby the bar is .retained in the notch in which it has been placed l as long as the cap is in position.

taining the discharge pressure at a constant value, is housed in a valve body |06 which is secured to the pump body I2 by the screws '46, and a valve head |08 secured to the main valve body |06 by the screws I I0.

The relief valve proper is of the poppet type comprising the disc ||2 with stem I|4 slidable in a hub II6 of the main body |06, the disc being beveled at I I8 and having a corresponding angular seat in the body which dividesv the interior of the body |06 into a suction chamber |20 includingall of the space above the disc |I2 and a discharge chamber |22 being the space belowthe disc. f

Ducts |24 and |26 in the pump and valve bodies respectively, connect the suction port 40 tothe suction chamber |20, while ducts |28 vanci |30 in the valve body and pump body respectively, connect the discharge chamber |22 to the discharge port 42. V

Depending from the valvfe head |08 into the suction chamber |20 is a long hub |32 internally chambered to contain the valve loading spring |34 andrl externally sized to slidably receive the valve spring cup |36 the bottom of which rests vupon a small knob |38 on the upper side of the 'y flange |44 resting on the upperface of the washer. The upper retaining washer |50 has a cen'- tral opening which passes over the screw head |42 loosely and rests on the ange |44. lA spring ring |52 is snapped into a groove at the upper edge of the washer |50, the groove'being positioned to hold the twol washers so spaced as to allow free turning movement of the flange |44 between them.l

The spring adjusting nut |54 is tapped to fit the external threads of the screw |40 and has af key |56 extending laterally intothe keyway |58 of thevalve head |08, whereby the nut is held nonrotatable when the screw is'turned, yet maymove freelyin an axial direction. The head |42 of the adjusting screw is provided with a deep screw driver slot '|60 in which When an adjustment of the spring |34 is to be made, the cap |10 is first removed, then, by the simple insertion of a screw driver into the screw slot |60, the locking kbar I62is made to rise out of its notch |66 of the washer |50 and the screw may be rotated until the desiredadjustment is attained, whereupon the locking bar ispushed into the nearest notch and the cap |10 replaced. In a situation where it may be necessary to reach into close spaces to make this adjustment, the desirability of this simple manipulation is obvious. limited, as it is on pumps of this class, a small portion only of the available height is taken by the adjusting and locking means, leaving space for a longer and more exible spring, whereby larger increments of adjustment may be made with smaller resulting variations in spring stress, making the matter of adjusting for fine variations in discharge pressure not dependent upon skillful or careful manipulation of the adjusting means. The use of a longer and more flexible spring also results in less variation in the discharge pressure at the various speeds of rotation and rates of discharge encountered in the operation of aircraft.

Now, as iswell known in the art, the suction head against which the pump `operates varies from oneV instant to the next because of aircraft acceleration, or deceleration, or altitude, or the fact that the fuel tank, when the craft climbs, may bewell below the pump, and when it dives, it may be well above it, `or vice versa, all depending upon the resp'ective locations of the pump and tank, so that, if an ordinary spring loaded relief valve only were provided, the constant rise and fall of. the pressure in chamber |20 would constantly influence the discharge pressure, because the sum total of effort acting against the spring to open -the valve would be the discharge pressure, acting to raise the valve from below,

added to the suction tending also to raise it but from above. Valves for use in this situation are therefore provided with a balancing means whereby variation in the suction does not add to nor subtract froml the forces tending to open the valve, and therefore does not affect the discharge strength. Around the edge of the central opening the material is thickened to provide a ring and'diaphragm from pulling apart in operation.

'the locking bar |62 is fitted snugly anq is hinged 75 |16 around which the upper edge of the spring cup |36 is so closely rolled as to form an air tight joint at this. point. and prevent the cup The diaphragm isalso made thicker at the outer edge to form the wedging ring I 18, this ring and a small portion of the diaphragm being Furthermore, where height is ,clamped between the valve body |06 and head out under the suction pressure in operation, but

not tight enough to cause cold 'ow.

The active portion |82 of the diaphragm is of U shaped cross section which loops downward between the outside of -the cup |30 and the inner edge of the annular rib |84 in the body |06.

Since the material composing the diaphragm swells appreciably from gasoline absorption, the loop |82 will drop downward more as the material swells. It will also be drawn upwardly farther as the valve rises to its maximum height. If then, the effective area of the diaphragm is to remain constant `under both of these extremes, the sides of the U loop must be so supported as to maintain a constant width under all conditions.

This condition will be met when lthe drop in the loop |82 and the width of the rib |30 is such that the sides of the loop will be held parallel and to a uniform spacing with each other in all positions. In such a structure the effective area of the diaphragm will be constant for any valve lift and for any degree of swelling of the material, and the discharge pressure will be unaffected by -these variations.

The space above the diaphragm, in the form of a chamber |80, is usually connected by a hole 80 to the atmosphere, but may be connected to the intake manifold when a supercharger is employed, by a pipe fitted to the pipe tapped opening |00, causing the fuel discharge pressure to increase directly with rise in manifold pressure.

Obviously, increased'suction in the chamber |20 will pull as much harder downwardly on the cup |30 as it does upwardly on the valve disc M2, and the valve closing pressure will be controlled entirely by the spring |34 independently of variations ln suction head.

into the holes in bosses 202. 'I'he bottom of the frame rests on the upper surface of the pump body v|2 whereby the frame is held securely in place as long as the valve body |06 and the pump body |2 are assembled but may be readily removed for` repairs to the valve when the pump and valve bodies are separated.

Torque springs 204, surrounding the hinge pin, have free ends which engage the frame and ap, the springs being tensioned to urge the flap to closed position.

Between the flap |92 and the seat 206 on the body |00 there is secured aV facing pad 208 of resilient material, preferably a compound of cork and synthetic rubber.V A retaining plate 2|0 lies on top of the facing, and rivets 2|2 secure the retaining plate to the flap with the facing between.

In order to provide against any distortion in the facing strip and to allow for the swelling inherent in the facing material, the facing strip is pro- A bypass valve is usually incorporated in the relief valve body of the power pump of aircraft fuel systems, so that, in the event of sticking of the power pump rotor, or other power pump failure, fuel may be forced through the power pump, independently of its pumping elements, by means of an auxiliary hand pump provided for the purpose.

Heretofore, these bypass valves have been made with a metal to metal seat, necessitating considerable initial spring pressure to hold'them closed when not operating, and have not been so placed as toy provide the greatest freedom in the passages through them, whereby considerable hand pump effort was required to overcome these innate resistances before hand pumping became effective.

The bypass valve herein disclosed is of improved design.' It is of synthetic rubber to metal seat construction, so that a Very light spring holds it closed effectively against leakage, and it is so placed and its orifices so shaped, as to provide a substantially direct nonresisting passage for the flow of the hand pumped fuel.

Referring to Figs. 1 and 5, a rectangular metal valve flap |92 having hinge ears |94 is swingably supported in the valve frame |06 by the hinge pin |98, the frame itself being supported in the body |06 by round end portions 200 extending slidably vided with spaced apart holes into which the spacing washers 2M fit freely, the center of the washers having holes for the rivets 2|2.

'Ihe washers are enough thicker than the facing strip, andrenough smaller in diameter than the holes inthe strip, that after assembly, the strip will be.

held between the ap and-the retaining plate with such degree of freedom that there will be no distortion even after the anticipated swelling has ltaken place.

Having described an embodiment of the invention in which the objects hereinbefore set forth are attained, I claim:

l. An adjusting and locking device comprising, a Athreaded member, an abutment nut threaded upon said member, said member having a headed portion provided at one end thereof with a peripheral flange and at its other end with a screw driver receiving slot, a looking bar rockably mounted within said slot and having an extended end, and a washer loosely disposed about said headed end and adapted to be fixedly held against rotation, said washer having a plurality of radially extending recesses on its inner periphery into any one of which said extended end of ,the locking bar may be inserted to hold said threaded member against rotation, and said locking bar being rockable out of such recess upon theinsertion of a screw driver into said slot to permit said threaded member to be rotated.

2. An adjusting and locking device comprising, a threaded member, a head at one end of said member having a screw driver receiving slot therein, a peripheral flange adjacent said head, fxedly mounted spaced apertured washer means of greater diameter than said peripheral ange,

said washer means having said threaded mem` ber slidably extending therethrough with the peripheral ange rotatably seated therebetween,

one of said washer means having a plurality of radial recesses on its inner periphery, and a locking bar rockably mounted in the head slot of said threaded member and having a portion movable into and out of said radial recesses.

3. An adjusting and locking device comprising, a threaded member, a head at one end of said member having a screw driver receiving slot therein, a peripheral ange adjacent said head, fixedly mounted spaced apertured washer members having said threaded member extending therethrough and the peripheral ange rotatably ,Y seated therebetween, the washer member adjacent the head of said threaded member having a plurality of radially extending recesses on its inner periphery, a planar locking bar pivotally,

mounted on the head of said threaded member within said screw driver receiving slot, said 1ock.

ing bar having a body portion extending beyond said .slot and terminating in an offset' end, said extending body portion of the locking bar being arranged to be rocked into and out of one of said radial recesses for locking and .unlocking the rotatable threaded member, and means arranged for mounting adjacent the head of said threaded member for restricting movement of the offsetend of said locking bar and maintaining the extending body portion of the locking bar in seated engagement with one of said radial recesses.

' 4. An adjusting and locking device comprising a hollow housing, a threaded qmember axially mountedon said housing for rotation, an abutment nut threaded upon said member, said member having a headed end provided with a screw driver receiving slot, a locking bar rockably mounted within said slot and (having an end ex-` tending beyond the head of said member, a

having a plurality of recesses for receiving the extending end of said locking bar, said threaded member being free for rotation when the extend# ing, one -of said washers having a plurality of radially extending recesses on its inner periphwasher member carried by said housing and 'v locking -bar pivotally mounted within said head slot and having a portion extending beyond said slot'for seating'engagement within one of the radial recesses on said one washer, said extending portion having an oiset end, an abutment nut having a key portion on its pheripheryy extendingimtothe wan slot in said Jmmsiungr and 7 threadedly receiving therethrough the threaded -member,'and a cap for said housing being closely spaced from the offset end of said locking bar for maintaining the extendingv portion in seated engagement within one of said radial recesses.

6. An adjusting and locking device comprising a tubular housing having an axial slot extending partially lengthwise along the inside thereof, a shoulder on the inner periphery of said housing 'adjacentone end thereof, an 'apertured washer seated on said shoulder, a screw member having .a threaded shank, a headed end and a peripheral flange therebetween, said threaded, shankl extending through said washer and the peripheral ange being rotatably seated thereon, an abutment nut threaded on said shank and having av peripheral key seatedwithin the axial slot of said housing, a second apertured washer loosely embracing the headed end of said screw member and being seated on said peripheral flange, a resilient ring seated insaid housing and against said second washer for maintaining the latter seated on said peripheral ange, a screw driver receiving slot in the headed end of said screw member, a planar locking bar pivoted to said headed end within said slot, said bar having a body portion extending beyond the end of said slot and termi- .nating in an oiset end, said second apertured member having a plurality of radially extending 1 notches or'i the inner periphery thereof into any ery, a threaded member having a transversely extending ilangel adjacent one end and rotatably seated between saidwashers, a head on said member extending throughsaid one washer and` having a screw driver receiving slot therein, a

one of which said extending body portion of the e locking bar may be inserted to hold said threaded member against rotation, and. a removable sealingcap on said one end of, the housing closely spaced from the offset endl of said locking bar for maintaining the extending body portion thereof in seated engagement within one of the radial recesses,

- RUSSELL R. CURTIS. 

